Closing system between a cap and a stator in an electric machine, process for closing between a cap and a stator in an electric machine and stator for an electric machine

ABSTRACT

A closure system between the cap and the stator in an electric rotating machine, wherein the stator (1) comprises at least one closure hole (1a) defining an inner wall (1b). The cap (2) comprises at least one contact portion (2a), the end of the contact portion comprising at least one through-hole (2c); the through-hole (2c) being substantially aligned with the closure hole (1a) when the end of the contact portion (2a) contacts the stator (1); and wherein a polymer (P) is injected through the through-hole (2c) in the inner wall (1b) of the closure hole. In the closing process of the present invention, the concentricity between the rolling bearing and the stator rotor accommodating bore is ensured by the fact that the geometry of the rolling bearing receiving portion (2e) allows the alignment to be made on the basis of the outer race (E) of the rolling bearing when it is already accommodated in the receiving portion (2e).

FIELD OF THE INVENTION

The present invention relates to a closure system between the caps of anelectric machine and a stator of an electric machine.

BACKGROUND OF THE INVENTION

Rotating electrical machines are widely known in the art, and basicallycomprise a static part (stator) and a rotating part (rotor). In asimplified manner, the stator comprises a plurality of plates stackedand pressed to form a block or package, known as the stator core. Theseplates are commonly called stator blades,

In some constructions of electric machines, the caps of the electricalmachine are attached to the stator block by rivets. This constructionrequires a careful observation of the concentricity between the cap andthe stator, so that the assembly is achieved within a suitable tolerancethreshold.

In addition to the matter of concentricity in the assembly, the rivetingprocess itself can cause shifts of the blades of the stator package dueto buckling of the rivets and/or reinforcements under the package duringthe pressing operation needed for the attachment. That is, the bucklingof the rivet can cause its lateral displacement towards the bladepackage, moving the blades towards the rotor and reducing the machineair gap.

Additionally, the efforts needed to deform the rivets compromise thecorrect positioning of the cap since the absorption of forces exertinglateral efforts may displace the cap from the correct position.

The present invention seeks to provide a closure system between the capand the stator in an electrical machine which eliminates the need for acomponent manufacturing process having a high dimensional accuracy.

The present invention also seeks to provide a closure system between thecap and the stator in an electrical machine that allows the attachmentof a cap manufactured by an injection process without this cap having tobe machined nor manufactured with high dimensional accuracy,

The present invention also seeks to provide a closure system between thecap and the stator in an electric machine which eliminates the need forriveting between the cap and the stator.

The present invention also seeks to provide a closure system between thecap and the stator which allows centralization of the assembly using theouter face of the rolling bearing as a reference.

The present invention also seeks to provide a closure process betweenthe cap and the stator in an electric machine which ensuresconcentricity between the cap and the stator.

The present invention also seeks to provide a stator for a rotatingelectric machine which enables the cap to be secured by the injection ofa polymer.

The present invention also seeks to provide a closure process betweenthe cap and the stator in an electric machine which eliminates the needfor rivets or other fastening elements.

SUMMARY OF THE INVENTION

The present invention achieves the above objectives by means of aclosure system between the cap and the stator in a rotating electricmachine, wherein the stator comprises at least one closure hole definingan inner wall; the cap comprises at least one contact portion, the endof the contact portion comprising at least one through-hole; thethrough-hole being substantially aligned with the closure hole when theend of the contact portion contacts the stator; wherein a polymer isinjected through the through-hole into the inner wall of the closurehole.

Preferably, the inner wall of the closure hole has at least one recess,and the contact portion is a leg whose end comprises a flat wall withthe through-hole.

The end of the leg may comprise a polymer receiving portion surroundingan edge of the through-hole.

The cap may further comprise a rolling bearing receiving portion forreceiving a rolling bearing having an outer race, with radiallyresilient central portion configured to exert pressure on the outer raceof the rolling bearing, the radially resilient central portioncomprising a plurality of wall segments arranged to form a circularcentral portion, and a plurality of connecting segments extendingbetween the circular perimetric portion and the radially resilientcentral portion.

The present invention also contemplates a process for closing betweenthe cap and the stator in a rotating electric machine, comprising thesteps of:

providing a stator comprising at least one closure hole and a rotoraccommodating bore, the closure hole defining an inner wall;

providing a cap comprising at least one contact portion and a rollingbearing receiving portion which receives a rolling bearing having anouter race, the end of the contact portion comprising at least onethrough-hole;

aligning the cover with the stator so that the outer race of the bearingis aligned and concentric with the rotor accommodating bore and thethrough-hole is aligned with the closure hole; and

injecting a polymer through the through-hole into the inner wall of theclosure hole.

Preferably, the step of aligning the cap with the stator is performedwith the aid of an alignment device.

The closing process may comprise simultaneously closing with two capsdisposed at axially opposing ends of the stator, wherein the two capsare aligned with the stator do that the outer race of the respectivebearing of each cap is aligned and concentric with the rotoraccommodating bore.

The present invention also relates to a stator for a rotating electricmachine, the stator comprising a plurality of stacked and pressed bladesand comprising at least one closure hole defining an inner wall, theinner wall having at least one recess.

In an embodiment, the recesses are formed automatically in the stampingprocess by punches having two different diameters and with the stackingperformed through turns of the stator blades.

Alternatively, the recesses may be machined in the inner wall.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1—is a perspective view of the caps and stator assembly of themachine according to an embodiment of the present invention; theassembly being positioned for closing;

FIG. 2—is a cross sectional view of caps and stator assembly of themachine according to an embodiment of the present invention; theassembly being positioned for closing;

FIG. 3—is a top view of the cap according to an embodiment of thepresent invention;

FIG. 4—is a top perspective view of the cap according to an embodimentof the present invention;

FIG. 5—is a bottom perspective view of the cap according to anembodiment of the present invention;

FIG. 6—is a schematic view of the polymer used by the closing system ofthe present invention, the polymer being illustrated as it would beafter solidifying; and

FIG. 7—is a schematic illustration of the closing between the upper capand a stator, an alignment device being also shown.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described hereinafter based on examples ofpreferred embodiments shown in FIGS. 1 to 7.

FIGS. 1, 2 and 7 the stator and caps assembly of a rotating electricmachine. FIGS. 1 and 2 show the assembly in the closed position, andFIG. 7 schematically shows the upper cap being engaged for closure.

FIG. 1 shows a stator core 1 formed mainly by a plurality of statorblades. The detailed construction of this kind of stator is known tothose skilled in the art and will not be discussed here.

The stator is preferably manufactured of steel, but other materialscould be used. As better shown in FIGS. 2 and 7, the stator has at leastone region with a closure hole 1 a. The closure hole 1 a defines asubstantially tubular inner wall 1 b. Preferably, the stator has fourclosure holes 1 a, and each hole is disposed spaced from one another,for example, at the corners of the stator 1.

Naturally, when the stator has non-rectangular blades, the holes arearranged in a spaced configuration in the vicinity of the edges of theplates.

As known to those skilled in the art, the stator also has a central bore1 d which accommodates the rotor.

An end cap 2 is fixed to each end of the stator core. The constructionof an end cap is known to those skilled in the art, so that the capfeatures which will be detailed are those relevant to the understandingof the inventive solution described herein.

Other components of the moving core of the electric machine—for example,rotor and shaft—are fully known to those skilled in the art andtherefore will not be described in detail herein.

As better shown in FIGS. 3 to 5, each end cap has at least one contactportion 2 a formed to contact the stator core 1 for closing (attachment)between the parts.

As known to those skilled in the art, the end cap has a central portion2 d which receives rolling bearings, such as ball bearings. For correctassembly of the electric machine, it is necessary to ensureconcentricity between the cap's rolling bearing and the region (centralbore 1 d) that accommodates the rotor in the stator.

In the closure system of the present invention, the end 2 b of thecontact portion 2 a comprises at least one through-hole 2 c. As shown inthe figures, the contact portion 2 a may comprise a leg 2 a and the end2 b may comprise, for example, a flat wall 2 b with the through-hole 2c. It should be emphasized, however, that the contact portion could be acontinuous wall or even spaced wall segments.

In the embodiment shown in the figures, each end cap has four contactlegs. However, the number of legs could be greater or lesser dependingon the design of the contact portion. Naturally, the number of closureholes of the stator may also vary, so that each contact leg correspondsto a closure hole of the stator.

Additionally, in the embodiment shown in the figures, the four contactlegs 2 a are arranged spaced apart such that each leg is close to eachof the stator core corners when mounting the assembly. In this case, thestator core has a corresponding closure hole in each corner,

Naturally, when the stator is formed by circular or non-rectangularblades, the contact legs 2 a will be arranged in spaced locations sothat they can match the stator holes.

During assembly for the closing between the stator 1 and the cap 2, thethrough-hole 2 c is substantially aligned with the closure hole 1 a.Thus, for the closure, i.e., for the attachment of the cap 2 to thestator 1, a polymer P is injected through the through-hole 2 c into theclosure hole.

The polymer used may be any suitable polymer such as, for example, theTechnyl® A 216 polymer. The polymer may be injected by any means knownin the art, such as with an injector arranged in the closing positioningstructure or with an independent injection device.

As best shown in FIGS. 3 to 5, the contact legs 2 a may have a polymerreceiving portion 2 d proximate to the through-hole 2 c. The receivingportion 2 d may take the form of a recess at the end 2 b, the recesssurrounding the edge of the through-hole 2 c.

Thus, for the locking, the polymer P fills the through-hole 2 c and thepolymer receiving portion 2 d, locking together the cap and the stator.

The injected polymer secures the cap to its position, so that thepolymer absorbs all variations in the positioning. In addition, with theuse of the polymer as a fastener, there is no need for riveting of theparts nor for the use of an additional fastening element (such as ascrew or the like).

As best shown in FIG. 2, in the preferred embodiment of the presentinvention, the inner wall 1 b of the closure hole 1 a has at least onerecess 1 c, Preferably, the inner wall 1 b of the closure hole 1 a has aplurality of recesses 1 c.

The recesses 1 c function as regions for anchoring the injected polymer,so that the differences in the coefficient of thermal expansion of thestator metallic material (steel) and plastic do not affect the dimensionof the assembly, avoiding relative displacements between the differentmaterials when heated due to the motor operating temperature.

The recesses 1 c may be formed in any suitable manner. For example, therecesses may be formed by machining

Preferably, the recesses are formed automatically in the stampingprocess by means of punches with two different diameters and with thestacking performed through turns of the stator blades. The amount ofstacked blades with each diameter type is variable as it depends on theprogramming performed during stamping and stator package formation.

In one embodiment, the stacking is performed in 90° rotations, butsmaller (e.g., 45°) or larger (e.g., 135°) rotations could also be used.

While in the embodiment shown in the figures the inner wall 1 b of theclosure hole 1 a comprises a plurality of circular recesses 1 c spacedapart in relation to the axis of the inner wall 1 b, it should benoticed that the recesses could have any shape and any spatialdistribution in the closure hole 1 a.

FIG. 6 shows the polymer P in the configuration in which it would beafter being solidified. Thus, upon injection and solidification, thepolymer P has a cylindrical wall P1 corresponding to the inner wall 1 bof the closure hole 1 a, shoulders P2 corresponding to the recesses 1 cof the closure hole 1 a, an enlarged end portion P3 corresponding to thepolymer receiving portion 2 d of the contact portion 2 a, and atransition portion P4 corresponding to the through hole 2 c of thecontact portion 2 a.

It will be understood that the closure process of the present inventionis that of assembly or closure between the cap (or caps) and the stator.Thus, the closing process comprises locking, attaching or mountingtogether the cap and the stator,

In the closing process of the present invention, the stator and the cap,or the caps, are disposed in a positioning structure having an alignmentdevice 3 (see FIG. 7).

The positioning structure, equipped with the alignment device 3, allowsassembly between the cap and the stator (when two caps are used, theassembly can be performed with the two caps simultaneously orseparately). The alignment device 3 determines the desired positioning(concentricity).

One of the main advantages obtained with the present invention is thepossibility of significantly improving the concentricity between thebearing and the rotor accommodating bore.

One of the factor that further improves this concentricity in theclosing system of the present invention is the fact that the geometry ofthe rolling bearing receiving portion 2 e allows the alignment to bemade with reference to the outer race E of the rolling bearing alreadyaccommodated in the receiving portion 2 e (see FIG. 7). That is, sincethe rolling bearing is visible on the cap, it is possible to align thestator bore 1 d with the outer race E of the rolling bearing itself,significantly improving concentricity.

To that end, as best seen in FIGS. 3 to 5, the rolling bearing receivingportion 2 e may comprise a radially resilient central portion 20configured to exert pressure on the outer race of the rolling bearing.

The resilient central portion 20 comprises a plurality of wall segments20 a arranged to form a circular central portion.

The elasticity or resiliency of the receiving portion is achieved by thegeometry of the cap which comprises a circular perimetric portion 21 anda plurality of connecting segments 22 extending between the circularperimetric portion 21 and the radially resilient central portion 20.

As can be seen in FIGS. 4 and 5, each connecting segment 22 comprises afirst end attached to the circular perimetric portion 21 and a secondsplit end, with a first portion attached to a first of the wall segments20 a of the radially resilient central portion 20 and a second portionattached to one adjacent of the wall segments.

The closing process comprises aligning, with the aid of the alignmentdevice 3, the cap 2 with the stator 1, so that the outer race E of therolling bearing is aligned and concentric with the rotor accommodatingbore 1 d and the through hole 2 c is aligned with the closing hole 1 a.The reference used for alignment is the outer race of the rollingbearing.

In that sense, as shown in FIG. 7, the alignment device 3 includesprojections 3 a, so that, upon alignment, each projection 3 a isdisposed between the two-part ends of the connecting element 22. In thisway, the tool is able to position itself in the vicinity of the bearingreceiving portion 2 e, so that the alignment is made with the outer raceE of the bearing received in the receiving portion 2 e.

It is important to note that although the closing process of the presentinvention requires the outer race E of the bearing to be aligned andconcentric with the rotor accommodating hole 1 d, it is sufficient thatthe through hole 2 c is aligned with the closing hole 1 a is enough toform a channel for receiving the polymer.

After alignment, the polymer P is injected through the through-hole 2 cinto the inner wall 1 b of the closure hole.

The cap 2 is formed in one piece from an aluminum injection process,however, any suitable material could be used.

Thus, the closure solution proposed by the present invention eliminatesthe need for rivets or other fastenings between the caps and the stator,while ensuring concentricity between the cap and the stator.

Having described examples of the preferred embodiments of the closuresystem of the present invention, it should be understood that the scopeof the present invention encompasses other possible variations of theinventive concept described, being limited solely by the wording of theappended claims, including the possible equivalents.

1. A closure system between a cap and a stator in a rotating electricmachine, characterized in that: the stator (1) comprises at least oneclosure hole (1 a) defining an inner wall (1 b); the cap (2) comprisesat least one contact portion (2 a), the end of the contact portioncomprising at least one through-hole (2 c); the through-hole (2 c) beingsubstantially aligned with the closure hole (1 a) when the end of thecontact portion (2 a) contacts the stator (1); in which a polymer (P) isinjected through the through-hole (2 c) into the inner wall (1 b) of theclosure hole.
 2. The closure system according to claim 1, characterizedin that the inner wall (1 b) of the closure hole (1 a) has at least onerecess (1 c).
 3. The closure system according to claim 2, characterizedin that the contact portion (2 a) is a leg whose end (2 b) comprises aflat wall with the through-hole (2 c).
 4. The closure system accordingto claim 3, characterized in that the end (2 b) comprises a polymerreceiving portion (2 d) surrounding an edge of the through-hole (2 c).5. The closure system according to claim 3, characterized in that thecap comprises a rolling bearing receiving portion (2 d) comprising aradially resilient central portion (20) configured to exert pressure onan outer race of a rolling bearing, the radially resilient centralportion (20) comprising a plurality of wall segments (20 a) arranged toform a circular central portion, a circular perimetric portion (21) anda plurality of connecting segments (22) extending between the circularperimetric portion (21) and the radially resilient central portion (20).6. A process for closing between a cap and a stator in a rotatingelectric machine, characterized by comprising: providing a stator (1)comprising at least one closure hole (1 a) and a rotor accommodatingbore (1 e), the closure hole (1 a) defining an inner wall (1 b);providing a cap (2) comprising at least one contact portion (2 a) and arolling bearing receiving portion (2 e) which receives a rolling bearinghaving an outer race (E), the end of the contact portion comprising atleast one through-hole (2 c); aligning the cap (2) with the stator (1)so that the outer race (E) is aligned and concentric with the rotoraccommodating bore (1 d) and the through-hole (2 c) is aligned with theclosure hole (1 a); and injecting a polymer (P) through the through-hole(2 c) into the inner wall (1 b) of the closure hole.
 7. The processaccording to claim 6, characterized in that the step of aligning the cap(2) with the stator (1) is carried out with the aid of an alignmentdevice (3).
 8. The process according to claim 6, characterized in thatit comprises providing two caps (2) at axially opposite ends of thestator, wherein the two caps (2) are aligned with the stator (1), sothat the outer race of the respective bearing of each cap is aligned andconcentric with the rotor accommodating bore (1 d).
 9. A stator for anelectric rotating machine, the stator (1) comprising a plurality ofstacked and pressed blades and being characterized in that it comprisesat least one closure hole (1 a) defining an inner wall (1 b), the wall(1 b) having at least one recess (1 c).
 10. The stator according toclaim 9, characterized in that the ate least one recess is formed bymachining the inner wall (1 b).
 11. The stator according to claim 9,characterized in that the inner wall (1 b) has a plurality of recesses(1 c) and the recesses (1 c) are formed automatically in the stampingprocess by means of punches with two different diameters and with thestacking carried out through turns of the stator blades.